I have a lot of recurring events from which I delete or change some single occurences regularly. In the past I always did the changes in Thunderbird, because doing it in Android it made several recurring event out of the one, which is very irritating and leads to mistakes in administering the events.
However, now only the main recurring event is being synchronized from Thunderbird to Android and all the individual changes don't appear on my phone at all. I am not sure when that started, but it could have begun with the last update to 3.2.1.2.